While direct climatic effect on individual species performance has been well documented, the importance of biotic interactions in modulating ecological responses to climate change is still poorly understood. Here, we coupled neighborhood modeling framework and plant functional tradeoffs to simultaneously investigate the direct and indirect effects of increasing climatic variability as well as an extreme climatic event (a 100-yr. ice storm) on long-term seedling dynamics in a subtropical forest.
Results/Conclusions
Our results show that (i) recent climate change caused pronounced turnover of seedling assemblages as a result of species-specific population fluctuations; (ii) species sensitivity to their conspecific and heterospecific neighbors were highly temporal dependent and explained a large amount of variation in decoupled seedling survival that was associated with the strength of storage effect; (iii) functional tradeoffs related to resource uptake and growth-strength strategies did interact with climatic change but only played a small role for uncorrelated species response to variable environments. Taken together, these results suggest that demographic decoupling was prevalent in our plot and neighborhood interactions play a dominate role in mediating the effects of climate change. Previous trait based studies may overestimate the direct effects of climate change as functional tradeoffs were also correlated with competitive balance among co-occurring species. Given that climate variability and extremes are predicted to increase in the future, our results suggest local species interactions may become more important in population persistence and species distributions, which may lead to rapid community-level reorganization, particularly in diverse forests. Thus, there is an urgent need to explicitly incorporate biotic interactions in process-based forest models that are used to predict ecological responses to global change.